Invited Talks -- Use of Enterprise Social Software to Support Organization and People Sensemaking -- Collective Intelligence in the Social Web -- Full Papers -- Robustness Analysis of Model-Based Collaborative Filtering Systems -- Phase and Coordination in Speech Production -- The Effect of Query Length on Normalisation in Information Retrieval -- An Evolutionary Neural Network Approach to Intrinsic Plagiarism Detection -- Investigation of Localised Centrality Metrics for Collaborative Networks: What Can They Reveal? -- Practical Development of Hybrid Intelligent Agent Systems with SoSAA -- Genetic Repair Strategies Inspired by Arabidopsis thaliana -- A Machine Learning System for Identifying Hypertrophy in Histopathology Images -- Creating Visualizations: A Case-Based Reasoning Perspective -- Assessing Context for Age-Related Spanish Temporal Phrases -- Using Shallow Natural Language Processing in a Just-In-Time Information Retrieval Assistant for Bloggers -- Towards Automatic Blotch Detection for Film Restoration by Comparison of Spatio-Temporal Neighbours -- Analysis of the Effect of Unexpected Outliers in the Classification of Spectroscopy Data -- Just Say It: An Evaluation of Speech Interfaces for Augmented Reality Design Applications -- SceneMaker: Intelligent Multimodal Visualisation of Natural Language Scripts -- The Enhanced Ranked List -- A Prediction Market for Toxic Assets -- Learning without Default: A Study of One-Class Classification and the Low-Default Portfolio Problem -- A Surveyof Recent Trends in One Class Classification -- Steady State RF Fingerprinting for Identity Verification: One Class Classifier versus Customized Ensemble -- An Analysis of Order Dependence in k-NN -- Norm Convergence in Populations of Dynamically Interacting Agents -- A Comparison of Word Similarity Measures for Noun Compound Disambiguation -- An Assessment of Machine Learning Techniques for Review Recommendation -- Buzzer - Online Real-Time Topical News Article and Source Recommender -- An Evaluation of the GhostWriter System for Case-Based Content Suggestions -- On Using Temporal Features to Create More Accurate Human-Activity Classifiers -- Demo Papers -- Physical Activity Motivating Games -- A Machine Learning System for Tracking Sentiment in Irish Economic News -- The Blogoduct System: A Just-In-Time Information Retrieval Assistant for Bloggers -- Sensing Handshakes for Social Network Development -- A Decision Support System for Energy Storage Traders.

This book constitutes the refereed proceedings of the 20th Irish Conference on Artificial Intelligence and Cognitive Science, AICS 2009, held in Dublin, Ireland in August 2009.  The  32 papers presented were carefully reviewed and selected for inclusion in the book. The topics covered are classification techniques, biologically-inspired computation, natural language processing, and applications of AI techniques for the social Web and financial markets.